Fluorescent tube



1941- J. w. MARDEN I 2,267,118

FLUORESCENT TUBE Fild March 1, 1940 INVENTOR J. 50. MfiEDE/V.

ATTO RNEY Patented 1)....23, 1941 FLUORESCENT runs John W. ltiarden, East Orange, N. .L, assign Westinghouse Electric & Mann! 1 pany, East Pittsburgh, Pa a c Pennsylvania orto Comrporaon-ot Application March 1, 1940, Serial No. 321,625

4 Claims.

The present invention relates to discharge lamps and particularly to what are known to the art as fluorescent lamps wherein the invisible radiations generated by the discharge excite a fluorescent coating and are converted into visible radiations.

It is the primary object of the present invention to provide a high emclency fluorescent lamp 'by shaping the envelope so as to enable the application of a greater quantity of average watts per unit area of envelope surface. Inasmuch as present type "fluorescent lamps are designed to operate from supply sources of the customary domestic potential, there is naturally a limit to the current and voltage which can be applledto the lampwithout destroying the lamp or shortening its useful life. I

In carrying out the present invention the portion of the envelope between the electrodes which surrounds the ensuing discharge is flattened so as to be of oval cross-section prior to its being coated with a fluorescent material. This may be more readily appreciated by reference to the accompanying drawing wherein:

Fig. 1 is a front view of a fluorescent lamp made in accordance with the present invention; Fig. 2 is a side view of the lamp shown in Fig. 1; v

Fig. 3 is a cross-sectional view taken on the line 111-111 of Fig. 2, and

Fig. 4 is a cross-sectional view similar to that of Fig. 3 but having its flattened sidewalls somewhat thickened to provide a lens eil'ect for the cathode dark-spaceto the other. A fluorescent coating I 3 lsprovided on theinterior surface of the lamp which is excited by the ultra-violet radiations generated during the discharge with the visible light from the coating being trans-' mitt-ed through the walls of the envelope, the color of the visible light being determined by the composition of the coating material, as is well known in the art.

Prior to sealing-oi? the lamp, ,2. suitable gas,v

such s argon, neon, or other noble monatomic a small quantity of mercury vapor. Upon the application of a suitable potential from a domespurpose of directing the emitted visible 'radiations.

Referring 'now tothe drawing in detail, :an envelope 5 is shown provided with oppositely disposed electrodes 8 and "l which, as shown, are of um, strontium, or the likepgiving a copious flow of electrons when heated. I

Leading-in and supporting conductors for the electrodes 6 and I extend througha press portion 8 at each end 01 the cylindrical portion of posed electrode; or. in other words, the flattened portion extends approximately i'rom one the coiled tungsten type and coated with an electronemitting material, such as the oxide of bari-' tic source'of supply of 115 or 230 volts and heating of the electrodes 6 and l, ionization of the starting gas occurs with a resulting discharge between the electrodes The discharge vaporizer.

the mercury within an extremely short period of time with the resultgthat the resonant lines of mercury which lie within the spectral range at about 2537 Angstrom will predominate.

Moreover, due to the oval configuration the "resonant radiations of mercury are generated near the flat side walls of the envelope 5 so that there is inappreciable reabsorptlon of such radiations by the mercury, resulting in greater excitation of the coating and an increase in the efllciency of the visible light. Inasmuch as the edges of the oval portion which have relatively sharp radii of curvature are the coolest portion of the lamp during operation, any condensation Also, v

of the mercury will occur at these edges. the. temperature at the edges necessarily determines the, vapor pressure, which thus allows operation of the lamp at greater average temperature than the optimum value, the latter of which isdependent upon the temperature at the coolest points. Moreover, because condensation of the mercury is confined to the cooler edges, the lamp is operable at a higher-voltage per unit length since the cathode drop remains constant, thus permitting the application of an increase in the average watts per unit area 01 envelope surface, all of which results in a higher emciency and a higher output of lumens per foot of lamp length.

A further advantage in the oval configuration resides in the fact that it causes themercury vapor to reach equilibrium in a very few minutes,

whereas if the coolest part of the tube was at the end,- the time required for the mercury to reach equilibrium would be so great as to be prohibitive.

If desired, the flattened side walls. which as a matter of fact naturally have a slightcurvature, may be thickened as shown in Fig. 4 so as to produce a lens effect to thus direct the visible radiations emitted by the lamp.

It thus becomes obvious to those skilled in the I art that a fluorescent lamp of high efllciency is mum excitation of the fluorescent coating. Also,

since the'curved edges of the: envelope are cool during operation of the lamp, the mercury vapor pressure is controlled to such an extent as to allow greater average temperature of operation together with an increase in-the average watts per unit area of tube surface with an attendant increase in efllciency of the lamp and a greater output of lumens per foot of lamp length.

Although one embodiment of the present invention has been shown and described, it is to be understood that other modifications thereof may be made without departing from the spiritand scope of the'appended claims.

I claim:

1.A gaseous electric discharge lamp comprising an envelope, electrodes in said envelope be tween which a discharge occurs upon the application of a suitable potential thereto, an ionizable medium in said envelope for sustaining the discharge between said electrodes and for generating high intensity radiations within the invisible portion of the spectrum, and said envelope being I of oval cross-section adjacent the ensuing discharge with its major axis of greater length than the diameter of the remaining portions to dispose the discharge in close proximity to the flattened side walls' to reduce self-absorption of the generated radiations to a minimum and to provide edges of sharp radii'of curvature having a lower temperature during operation of said lamp to cause an increase in the average temperature immediately adjacent the discharge and an increase in the wattage per, unit area of envelope surface with an attendant increase in the efliciency of said lamp.

2. A gaseous electric discharge lamp compris-' of said envelope between which a discharge oc-' close proximity to the flattened side walls to reduce self-absorption oi the resonant radiations of mercury to a minimum and to provide edges of sharp radii of curvature having a lower temperature during operation of said lamp to en-' able condensation of the mercury vapor at said edges and to prevent an increase in the mercury vapor pressure in the vicinity of the discharge with an attendant decrease in the eiflciency of said lamp.

3. A gaseous electric discharge lamp comprising' an envelope, electrodes disposed at the ends of said envelope between which a discharge occurs upon the'application of a suitable potential thereto, an ionizable 'medium.in said envelope for sustaining the discharge between said electrodes and for generating high intensity radiations within the invisible portion of the spectrum, said envelope being of oval cross-section-adjacent the ensuing discharge with its major axis of greater length than the diameter of the end portions to dispose the latter in close proximity to the flattened side walls to reduce self-absorption .of the generated radiations to a minimum and to provide edges of sharp radii of curvature having a lower temperature during operation of said lamp to cause an increase in the average temperature immediately adjacent the discharge and an increase in the wattage per unit area of envelope surface with anattendant increase in the efficiency of said lamp, and a fluorescent coating on the surface of said envelope for con--' curs upon the application of a suitable potential thereto, an ionizable medium in said envelopeincluding a gas to facilitate starting and 'mercury vapor for sustaining the discharge between said electrodes and for generatingv high intensity radiations within the invisible portion of the spectrum, said envelope being of oval cross-section adjacent the ensuing discharge with its major axis of greater length than the diameter of the end portions to dispose the dis-' charge in close proximity to the flattened side walls to reduce self-absorption of the resonant radiations of mercury to a minimum and to provide edges of sharp radii of curvature having a velope and excitable by the mercury radiations for converting the latter into visible light of 

